I had the same issue on one of ours, put new batteries in same result, tested charging system and not charging, removed charger and opened up, there was a ceramic cyclinder fuse inside that was blown, replace and put back together worked just fine although the charger hummed very louldly, issue with blown fuse in charger I do believe was due to charger was severely rusted, mother board included, which leads to believe there may be a short in it, jacked worked for 2 months and now same result, so now I'm just going to replace the charger and be done with it, charger runs $410 on Amazon